The operating state of a valve must often be known for proper operation of a device in which the valve is used. One way to monitor a valve's operating state is with a mechanical connection to a valve component, such as a valve body. However, conventional mechanical connections to valve components require seals that must prevent leakage, yet allow the connection to operate. In valves handling extremely aggressive fluids, seal connections create a risk of damage to other components if the seal connections fail. Thus, it is desirable to use an operating state indicator that does not require such a mechanical connection and its associated seals so that the risk of fluid leakage can be reduced, if not eliminated.
Some prior art remote indicating systems rely on magnets mounted on the valve bodies. While these function satisfactorily in most environments, the magnets can be destroyed in more hostile environments. For example, the hydrazine used in dual-fuel thruster systems can corrode such magnets. There is, therefore, a need for a remote valve status indicating system that does not rely on magnets exposed to the fluid controlled by the valve for which the system provides information.
Additionally, the stroke required by prior art valves to activate their switches requires large valve envelopes or housings. This increases the size of the valve, which results in increased weight and cost. In spacecraft applications, the increased size and weight reduce the amount of payload that can be carried by the spacecraft or increase launching costs. Thus, there is a need for a magnetic switch activation system that allows a valve with a shorter stroke to be used.